There is a special bind procedure for some models of powersafe RXers. It typically involves using a second battery. The procedure is way over complicated. But it does work reliably. I have two AR 9210s (powersafes) with telemetry and had a heck of a time getting them to take a bind correctly. Eventually, they came out with the "second battery bind procedure".
You can typically bind w/o following their procedure. But, how long you press the Bind button is critical!. Maybe that is why HH very quickly stopped selling some of these powersafe models. I am not overly happy being stuck with two over $400 rxers that are difficult to bind and have proven unreliable to keep the bind and are no longer available after less than a year.